In conventional asphalt paving operations, a self-propelled vehicle, known as a tractor, is used having a hopper on the front end thereof. The hopper receives asphalt paving material, typically from a dump truck. The asphalt material is transferred from the hopper to the roadbed or other surface being paved in front of transversely extending screw augers. A roadbed or other surface to be paved will be referred to the “reference surface” herein. The augers transport the asphalt material laterally in front of an elongated plate, or “screed”, which compresses and compacts the asphalt downwardly to form a “mat” of paving material, ideally of uniform thickness and surface finish.
The screed is typically pulled behind the tractor by tow bars that may allow the screed to may move upwardly or downwardly with respect to the tractor. The tow bars may be pivotally connected to the tractor and may pivot about an axis, or “tow points”. This arrangement effectively allows the screed to “float” with respect to the tractor as the screed is towed behind the tractor.
A conventional screed is of a set width. However, in certain paving applications, such as driveways, parking lots, and the like, varying the asphalt mat width is required. As a result, width-adjustable or extendable screed arrangements have become common for varying the width of the asphalt mat without interrupting the paving process. Typically, extendable screeds consist of a main screed section of a fixed width and hydraulically extendable “screed extenders” that are capable of extending from each end of the main screed section. Both extendable and non-extendable screeds may be equipped with endgates that act to maintain the asphalt material between the endgates and in front of the screed and screed extenders and not allow the asphalt material to migrate laterally past the endgates.
In a normal operation of an asphalt paver, an operator makes adjustments in the attack angle of the screed to affect the depth of the asphalt mat being laid. To maintain the asphalt material between the endgates as the screed attack angle is adjusted, the endgates may be extended or retracted with motorized or manually operated jacks. Further, many paving machines include two jacks coupled to each endgate for more accurately maintaining the correct positions of the endgates with respect to the screed extenders or screed, if no screed extenders are provided. The correct position of the endgate is a sliding contact with the reference surface, or the surface being paved. Also, an endgate may need to be extended to ride on top of a curb, while the surface next to the curb is paved.
When the asphalt mat thickness changes incrementally, the endgates, which are typically coupled to springs, may automatically adjust to float at the new paving depth. Because the endgate springs provide only a limited range of vertical motion to the endgates, operators of screeds must continually adjust the endgate height to maintain the endgate springs at or near the spring setpoint by rotating the endgate jacks, which controls the compression and extension of the endgate springs.
By keeping the endgate springs at or near their setpoint, the endgates can “float” as the main screed and the screed extenders come in to contact with various surface grades. If the mat being laid becomes too thick, the endgate springs may reach full extension, resulting in the endgates being lifted off the reference surface. If the mat being laid becomes too thin, the endgate springs may reach full compression which may limit the ability of the screed to float on the thinner mat.
Accordingly, there exists a need for a reliable and easy to use system and method for adjusting the heights of endgates of paving apparatuses.